Scaring mosquitos prevents reproduction

University of Haifa researchers discover warning signal.

By JUDY SIEGEL-ITZKOVICH
mosquito 298 (photo credit: Cunter Muller/ Hebrew University)
mosquito 298
(photo credit: Cunter Muller/ Hebrew University)
Female mosquitoes have been “tricked” into not laying their eggs by University of Haifa researchers, who have isolated the natural chemicals released by their enemies that serve as a warning signal that reproducing is too dangerous.
Described by the scientists as a “breakthrough,” the discovery will soon be published in the prestigious journal Ecology Letters. The technique may prove to be an effective way of fighting mosquitoes without using pesticides.
The natural compounds released by mosquitoes’ natural aquatic predators were identified for the first time in the lab of Prof. Leon Blaustein, who worked with an interdisciplinary team that included Ph.D. student Alon Silberbush; Dr. Shai Markman, a chemical ecologist from University of Haifa-Oranim; Dr. Efraim Lewinsohn and Einat Bar, chemists at the Neveh Yaar Research Center; and Prof. Joel Cohen, a mathematical and population biologist at Rockefeller and Columbia Universities in New York.
Previous research from Blaustein’s lab showed that the mosquito species Culiseta longiareolata chemically detects a voracious predator of its offspring in the water that is known as the backswimmer, Notonecta maculata. The mosquito avoids laying eggs where it detects the predator. But until recently, the chemical identity of these compounds was not known.
Ecologists and evolutionary biologists have long known that many prey species can detect predators chemically and, upon detection, take various actions to avoid being eaten or having their progeny eaten, but they were unable to determine the makeup of these chemicals.
By screening and comparing the chemicals released by N. maculata with those produced by Anax imperator, another aquatic predator that does not elicit a chemical response by the mosquito, they were able to narrow down the potential chemicals that elicited the mosquito’s behavioral response.
Blaustein’s group then conducted outdoor experiments on potential chemicals and determined that two of the chemicals released by the N.
maculata – n-tricosane and nheneicosane – repelled these mosquitoes from laying eggs and together had a synergistic effect.
Blaustein, who received funding from the Israel Science Foundation, suggested that spraying such synthetic compounds at mosquito breeding sites could not only result in much fewer mosquitoes in the immediate area but probably reduce mosquito populations overall.
Forcing pregnant mosquitoes to look for an enemy-free breeding site could mean they will die before laying their eggs.
The average mosquito has a 20 percent probability of dying as each day passes.
In addition, by concentrating their eggs in considerably fewer breeding sites that they regard as predator-free, the mosquito larvae would face increased competition, resulting in fewer and weaker emerging adults.
Blaustein explained that in the fight against mosquitoes, there are essentially three strategies. The preferred one is to prevent the emergence of adult mosquitoes at aquatic breeding sites. When this has not been done effectively, mosquito control workers try to kill the adults that have spread to residential areas. This is, of course, much more expensive and difficult and usually requires spraying chemical pesticides that pose environmental and health dangers.